For awhile I had a crosswise rail bike rack that had about a 500lb capacity & fit into a large hitch receiver. It would swing down on one end to load. I couldn't push the bikes up the slope,so got rid of it.
Speaking of steep slopes, a neighbor with a huge 1800cc cruiser bought the cheapest possible, assemble yourself, Harbor Freight Trailor. I told him how hard it would be to load the bike with that high a trailer & heavy bike. soon after both bike & trailer were gone - wonder if he dropped it?
I have owned a stand-up KENDON bike trailer for awhile. It has an under slung torsion bar axle, & car wheels. It is no more than 12" off the ground & easy to load. It also folds in the middle & will stand straight up in any garage. It has castors & only takes up about 5' X2'. Hardly know its behind a vehicle when pulled. Check them out on Ebay used, they are REAL nice.